1. Field of the Invention
The present invention relates to a secondary battery module including a plurality of rod-shaped battery cells arranged in a single casing, and a secondary battery module apparatus including such a plurality of secondary battery modules.
2. Description of the Related Art
With conventional techniques, lithium-ion secondary batteries have been employed in compact-sized devices such as personal computers, cellular phones, etc., because the lithium-ion secondary batteries provide a high power density. In recent years, such lithium-ion secondary batteries have begun to be employed in HEVs (hybrid vehicles) or EVs (electric vehicles). Also, such lithium-ion secondary batteries are anticipated to be employed as power smoothing rechargeable batteries in facilities for power generation such as solar power generation, wind power generation, etc., in which the power output is unstable.
In a case in which the secondary batteries are employed as such power storage rechargeable batteries, the power system includes a battery or a module assembly obtained by combining a plurality of unit batteries or cells. Power storage rechargeable batteries are known having capacities ranging from several kW up to several hundred kW or more. As the capacity of the rechargeable battery increases, the amount of heat generated by the cells becomes greater. Accordingly, there is a need to release the heat with high efficiency.
In general, in order to spread the secondary battery in usage of power storage rechargeable battery, the secondary battery modules are necessitated to be made with small size. In particular, in a case of employing a high power-density lithium-ion battery, there is a need to design such a module with a compact size in order to take the advantage of the high power-density lithium-ion battery. Furthermore, there is a demand for a compact module structure configured to reduce the irregularities in the temperature of the cells in the module. For example, a module structure of a battery module for an EV (electric vehicle) has been proposed as described in Japanese Patent Application Publication No. 3524237.
In the module structure described in Japanese Patent Application Publication No. 3524237, a plurality of cells in a casing are supported by ribs such that they are arranged along the horizontal direction, and vents are formed in a top casing and a bottom casing. Thus, the cells are cooled by air flowing through the casing in the vertical direction.